As it turns out, production assistant Rutler had been plotting a proposal before Aguilera discovered the baby news. The pregnancy "wasn't expected, but it also wasn't unwelcome. They are all very excited though! Christina loves being a mom," a source reveals.

A second insider reveals that Rutler had been "working on the ring for over a year," and was hatching his proposal plan for several months -- finally popping the question two days before Valentine's Day, on Feb. 12.

"He wanted to do something that had meaning for both of them," the pal continues, explaining that Rutler chose to propose in the backyard of their new home -- which is still under construction -- around 7pm. "It was after sunset when everything is quiet and dark and it's turning into night," the friend reveals. First, he showed Aguilera a newly-planted Cherry Blossom tree (her favorite flower) on the grounds. Then, dressed in a suit, Rutler (who met Aguilera on the set of her 2010 film Burlesque) asked for her hand in marriage in a gazebo, surrounded by candles and hundreds of red roses.

Crying as he proposed, Rutler took his bride-to-be by surprise. "She was completely taken aback. She had no idea that he was going to propose then," the pal says. "She was shocked."

She said yes, and the couple then went to the home where they're currently staying -- where close friends and family surprised her again with an engagement party planned by Rutler. "It was a great night."